Method of producing photogravure plates



Patented Mar. 14, 1933 PATENT OFFICE AXEL A. PEARSON, OF KANSAS CITY,MISSOURI METHOD OF PRODUCING PHOTQGRAVUBE PLATES No Drawing. Applicationfiled July 13,

This invention relates to the process of producing photogravure platesto be used in making photogravure prints, and the invention contemplatesprocesses which are dirooted to two distinct methods, each of which isused to produce a particular type of plate.

The primary object of the instant invention is to provide a series ofsteps in a process of producing photogravure printing plates whichobviates the necessity of using the commonly known gravure tissue, whichprocess includes the employment of two distinct transparent positivesapplied in the process in a manner to create on the metallic printingplate, two superposed coatings,-the

' first layer performing its acid-resistingfunction and, combining thisfunction with the other coating, which is fluid-penetrable,

in a unique manner to produce an especially high grade gravure platewhich requires a minimum amount of re-touching.

A yet further object of the instant invention is to provide a newprocess of producing photogravure printing plates which may be practicedby those less skilled in the art, and which allows for the production ofa more perfect printing plate within a time much less than that nowrequired for the making of plates of this character.

' One of the objects of the invention is the provision of a process forproducing a duotype photogravure printing plate, .wherein is an areahaving no middle or half tones,

but which is present for the production only of lettering or similarareas of deepshadows formed upon a white or high-light background. Thisspecific phase of the invention is particularly novel in that the high-40 light or white ground around the lettering or deep shadows is alwaystrue, the outline is clean cut, and there are no ragged edges present.This particular area of the plate is for the purpose of what might becalled typographical printing, which printing is to be donesimultaneously with the production ofthe printing of the photogravure,,and the invention here contemplated applies to this area to a furtherextent in that there are permitted no foul bites.

1931. Serial N0. 550,622.

Since the ordinary process of producing photogravure printing plates iswell known in the art, and since, also, the steps in well knownprocesses are clearly and definitely set down in many existing patentsand publications, it will be necessary herein to illustrate only theconventional lnstrumentalities utilized in the process.

The steps in the well known and common process of producing photogravureplates consist in brief of the following:

1. Photographing the image to be reproduced in photogravure to makea'continuous tone negative.

2. Make a transparent positive from this negative.

- 3. Apply by printing upon the well known sensitized gravure tissue anordinary cross line gravure screen (contact printing).

4. Contact print the positive made in step 2 upon the gravure t ssueupon the cross line just printed thereon.

5.' Transfer the emulsion or coating from the gravure tissue to a copperbase or plate and peel off the'tissue sheet.

, 6. A copper base with emulsion adhering ghereto is developed andwashed until ready or use.

7. After drying, the copper plate having the developed emulsion thereoncarrying -a reproduction of the image to be reproduced is submerged inetching fluid and made ready for the application of ink.

These steps'are understood and are set down merely to make clear'theimprovement and advantage inherent in the process contemplated by thisinvention. Explanation of the process of producing photogravure borderwhereby no etching is ever allowed at the opaqued area and a beareris'formed.

The next and third step is to produce a transparent positive from eachof the negatives made as in steps one and two. These positives may be onfilm or glass and the same'are developed and dried in ordinaryphotographic fashion.

The fourth step in this process of producing 'photogravure printingplates is to produce a pre-coated copper plate which is to be the actualprinting plate. The coating is a sensitized film of solution, againstwhich the screened positive is placed and light passed therethrough tothe sensitizing of the copper plate as the ordinary contact exposure ismade.

After such printing, the exposed copper plate is developed, which actionproduces a printing plate having an acid-resisting ground, which groundhas the image to be reproduced formed as a part thereof, and, inaddition, a well defined screen over all areas in opaque which actuallyperforms the duty of masking to set off, upon the copper plate, welldefined areas which confine the etching action and serve as a wipingbearer during printing.

After this particular step just mentioned has been completed, theinvention requires that another sensitizing coat be flowed upon thecoating now on the copper plate. This superimposed sensitized coating isallowed to dry, after which the continuous tone positive is contactprinted thereupon. That is to say, light is passed through thecontinuous tone positive to act upon the second sensitized coating,after which developing of the second coating must take place to producea coating of varying thickness which directly overlies the firstcoating, and which is devoid of screen markings of any nature. When thisstep of printing the continuous tone positive takes place, it isabsolutely necessary that the lines of the image to be reproduced becaused to register exactly. It is notable at this point that the lastmentioned superimposed sensitized coating is used in lieu of gravuretissue, 'the use of which so often creates trouble in the rapidproduction of photogravure plates.

As the next step, the copper base now having two coats of resistingmaterial thereon is etched in a solution of copper dissolvent whichattacks and eats out the copper plate to different depths for thepurpose of forming ink pockets to receive the ink when the plate is inactual use. i

The advantages of the process just set down here becomes apparent whenan understanding is had of the action upon the copper plate by thedissolvent. In practice it is found that the dissolvent acts upon theplate to different depths, depending upon the thickness of the lastcoating of resisting material which was produced. The thinner portionsof this last resist allows the copper dissolvent to reach the lowermostcoating first, where it is confined to areas set off by the well definedscreen above described.

When the dissolvent reaches an area confined by said screen it isdefinitely masked or separated into zones, and the copper plateintensely attacked over this set off area. This action is carried outthroughout the entire face of the printing plate, all commensurate withthe thickness of the top coating and confining qualities of the first orlowermost coating;

After etching as above, the second or top coating is washed off, leavingthe first or lower coating present which may be utilized for procuring aproof which in turn may disclose any need of local reetching with brushor the like. This lower coating is then removed.

Obviously, ink pockets are effectively controlled through the processjust set forth and it is to be seen that a finer graduation of tone ispossible. The expense of producing such plates is less than the ordinarywell known method or process now in use and spoilage is reduced topractically nothing. Handling and retouching the plate in preparationfor actual use is obviated and in all, the process produces a result notattained in any known manner.

Where a print is to have thereon a typographical area or an area limitedto high lights and deep shadows, and where it is desirable to print theentire plate including both this area and the area including all tonesfrom high lights down to shadows, it is appropriate to use the processjust defined and to supplement the steps of this process by a treatmentas follows: I

Step 1 in this process is the same as step 1 next above, but thelettering or typographical area is blocked out with black paper having ascreen marked thereon so that the negative which reproduces the imagewill have a substantially clear area marked throughout by a well definedscreen. Step 2 likewise includes photographing the image to bereproduced with a screen in front of the plate to make a screenednegative. At this point this screened negative is acted upon to theextent of removing therefrom all of the coating or emulsion lying withinthe typographical'area. Here an additional step is to be followed whichconsists of making a regular line negative of the lettering which is toappear in the typographical area, said negative being large enough toinclude all of the area in question. In any desired manner this linenegative of the typographical area' is placed in position at the properpoint, or exactly where the emulsion of the screened negative wasremoved for this purpose. Thus a built-up negative is produced.

, Step 3 includes, as hereinbefore set down, the production of atransparent positive from each negative. It is to be remembered at thispoint that one of these positives will have the typographical areawithout lettering of any character but with the screen thereon, theother positive which is made from the built-up negative will have thetypographical area with the desired lettering and with an overlyingscreen. From this point on the relation between the two positives andthe metal printing plate is the same. When the plate is finally producedthe white ground around the lettering in the typographical area will betrue, there will be no ragged edges around the letters, and the letterswill have a clean cut outline the same as though they had beenseparately printed.

This last method is unique in that the face of the letters in thetypographical area will not have screen markings extending as high asthe area around the letters. The application of ink to the depressedloreaten out part of the printing plate which is to form the letter itselfis, however, provided with a screen tooth extending upwardly from thebottom of the pockets just sufficient to create gripping members so thatregardless of the size of the face of the letters, the ink will bepositively and uninterruptedly applied and no voids will be left whenthe offset takes place.

For obtaining plates engraved in relief, for typographic printing, theprocess is the same as just described for making printing plates,engraved in intaglio, but in that case negative originals are used.

While the precise technique of making photogravure printing plates hasnot been set 'down in detail, it is to be understood that the processhas been made clear beyond a doubt through the foregoing description.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. The process of producing photogravure printing plates which comprisestwice photographing the image to be reproduced to make a continuous tonenegative and a screened negative; producing a transparent positive fromeach negative; exposing the presensitized printing plate to lightpassing through the screened positive; developing said plate toestablish an acid-resisting coating; sensitizing said printing platedirectly over the coating; exposing said last sensitizing coating tolight passing through the continuous tone positive, with the images on.

the plate and'continuous tone ositivein register; and then etching saiprinting plate in a solution of co per dissolvent.

2. The process of pro ucing photogravure printing plates which comprisestwice photographing the image to be reproduced to make a. continuoustone negatlve and a screened negative; producing a transparent positivefrom each negative; exposing the pie-sensitized printing plate to lightpassing through the screened positive; developing said plate toestablish an acid-resisting coating having areas set off by well definedscreen markings; again sensitizing said printing plate directly over thesaid coating; exposing said last sensitizing coating to light passingthrough the continuous tone positive, with the image of the plate andcontinuous tone positive in register; developing the last coating toproduce an acid-resisting coating of varying thlckness superimposed uponsaid first coating; and etching said printing plate in a solution ofdissolvent, said etching solution penetrating the said plate aspermitted by the last proin register; the lowermost {coating beingformed through the said positive made from said screened negative, thetop coating being formed through the said positivemade from thecontinuous tone negative, both coatings being developed before etchingsaid plate whereby said etching action is confined to definite areas andcaused to act to varying relative depths.

4. The process of producing photogravure printing plates having an areathereon limited to high lights and deep shadow tones which com risesphotographing the image to be repro. uced with said area thereon coveredwith a sheet of black material having a screen marked thereon to make acontinuous tone negative; again photographing the same image through aregular screen to make a screened negative; removing from said screenednegative the area defined by said black material; making a linednegative of said area only and insert in space created by removal of thesaid area on said screened negative; producing a transparent positivefrom said continuous tone negative and said screened negative asaltered; and then producing a printing plate from said transparentpositives.

5. The process of producing photogravure printing plates having an areathereon limited to high lights and deep shadow tones which comprisesphotographing the image to be reproduced with said area thereon coveredwith a sheet of black material having a screen marked thereon to make acontinuous tone negative; again photographing the same image through ascreen to make a screened negative; removing from said screened negativethe area defined by said black material; making a lined negative of saidarea only and insert in space created by removal of the said area onsaid screened negative; producing a transparent positive from saidcontinuous tone negative and said screened negative as altered; exposingthe pre-sensitized plate to light passing through said screenedpositive; treating by developing said plate toproduce an acid-resistingcoating; re-sensitizing said plate over said coating; exposing saidre-sensitized plate to light passing through said continuous tonedpositive; and then subjecting said plate to A the same image through aregular screen to.

etching action whereby the deep shadow tones of said area are unbrokenby screen lines and said highlight portion is free of ink supportingpockets.

6. The process of producing photogravure printing plates having a areathereon limited to high lights and deep shadow tones which comprisesphotographing the image to be reproduced with said area thereon coveredwith a sheet of black material having a screen marked thereon to make acontinuous tone negative; again photographing make a screened negative;removing from said screened negative the area defined by said blackmaterial; making a lined negative of said area only and insert in spacecreated by removal of said area on said screened negative; producing atransparent positive from said continuous tone negative and saidscreened negative as altered; and then producing a printing plate fromsaid transparent positives by exposing the pre-sensitized plate to lightpassing through the screened positive and said continuous tone positive,and then etching said plate.

7. The process of producing a photogravure printing plate which consistsin applying to a screened negative ground on said plate, a sensitizedcoating; exposing said coating to light passing througha continuous tonepositive of the same image, the images of both negative and positivebeing in register as exposure is made; developing the exposed sensitizedcoating to create a film of varying thickness over said screenednegative ground; etching said plate in a solution of dissolvent, saidetching solution penetrating the said plate as permitted by said film ofvarying thickness and the spaces between the acid resisting ground ofsaid screened negative; and removing said film of varying thickness andsaid screened negative ground from the plate.

8. The process of produclng photogravure printing plates which comprisestwice photographing' the image to be reproduced tizing said plate overthe face of said plate over said spaces of like area; exposing said lastsensitizing coating to light passing through the continuous tonepositive; developing said last coating to produce a fluidpenetrablecoating of varying thickness overlying said acid-resisting coating;etching said printing plate in a solution of dissolvent to produce amultiplicity of spaces of like area throughout the face. of said plate,said spaces varying in depth to re- .tain varying volumesof ink when theplate is used in printing.

In testimony whereof, I

hereunto aflix my signature.

AXEL A. PEARSON.

